DE2219506A1 - Method of increasing the porosity of polyvinyl chloride resin - Google Patents

Description

"Method of increasing porosity of polyvinyl chloride resin

The use of acyclic organic azo compounds as catalysts for polymerizing ethylenically unsaturated monomers which undergo addition polymerization has been known for some time. In particular, U.S. Patent 2,471,959 discloses several aliphatic azo compounds having an acyclic azo group having individual tertiary carbon atoms bonded to each nitrogen atom, with. one of the carbon atoms which are bonded to each of the tertiary carbon atoms, the other valences are only satisfied by oxygen or nitrogen. Specifically disclosed is the compound ^ ^ ¹ -Azobis Gjyjjf-dimethylvaleronitrile), hereinafter referred to ^{as 11 ABVIf ".}

They are also peroxide type catalysts for the polymerization of vinyl chloride monomers in suspension polymerization reactions are well known. Examples are lauroyl peroxide and benzoyl peroxide catalysts are well known in the commercial Production of polyvinyl chloride resin (hereinafter also referred to as "PVC"), 'heat and the above catalysts are used as polymerization aids and the suspension is during the course of the reaction by agitation and generally by stabilizing the system with appropriate suspension stabilizers maintain

Ks have been dispersants or surface active agents since

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The earliest polymerization processes have been used to recover individual polymer particles from the suspension reaction mass to ensure. It was observed that the use of surfactants was useful in preventing the maintain proper porosity and dry mix properties, especially when used in conjunction with specific suspending agents. Correct porosity and Densities of the vinyl polymer particles are of particular concern and depend on the end use for which the resin is used should be, from. For example would be for applications that do not involve plasticizer absorption, such as for hard calenders and -extruding, vinyl blow molding and the like a dense, non-porous Particles with a narrow particle size distribution and superior powder flow properties are desirable. on the other hand would be for applications where plasticizer absorption is essential and where it is desired that as great an amount as possible be used is absorbed without affecting the powder plating properties of the resin, a highly porous resin is more desirable, for example when plasticizer is mixed with the resin particles and after a rolling mill for making polyvinyl chloride sheets fluid-conveyed. is.

The US Patent 3 4-59719 discloses the use of 2,2'-azobis-isobutyronitrile initiator in combination with polyvinyl pyrrolidone as a suspending agent for suspension polymerization of polyvinyl chloride with vinyl acetate ^v at a temperature in the range of about 75 ° to 95 ° C, which allows the formation of a glassy, spherical, non-porous particle with a high bulk density and a narrow particle size distribution.

U.S. Patent 2,857,367 describes suspension polymerization of vinyl chloride, being a combination of a primary dispersant, namely dextran (dextran), and a secondary dispersant, one of which is sorbitan monolaurate, under acidic conditions used to make a resin particle with a density of 0.40

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up to 0.45 6 per ecm.

The above-mentioned patents and other prior publications consistently teach that a secondary dispersant is required to achieve an increase in porosity. This is generally true with known catalysts for the suspension polymerization of PVC, with one exception from ABYN, which supplies a PVC earζ of moderately high porosity, when used alone under the critical conditions specified below. In other words it was found that ABVN catalyst under certain conditions the porosity increases without the involvement of a secondary dispersant.

It has been found that the use of ABVN in conjunction with comparatively small amounts of sorbitan monolaurate in a suspension polymerization process for polyvinyl chloride resin unexpectedly provides a porous resin particle with a comparatively narrow pore size distribution. This is particularly surprising since another catalytic azonitrile, namely ^, ^ ¹ -azobis-isobutyronitrile, provides a dense, non-porous particle.

The use of less surfactant results in faster reaction rates and a more uniform one Reaction exotherm in a given catalyst system because the surfactant is inhibitory Has properties. The average pore size in the range of about 0.3 to about 0.5 microns and a porosity in the range of 0.35 "to about 0.50 cc / g ensures the Absorption of enough 'plasticizer to process the Resin without impairing the fluid transportability of the resinous iuasse to facilitate.

Yet another unexpected result of using ABVN in connection with sorbitan monolaurate is that a

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get more uniform reaction exotherm in the reaction vessel will. At the same time as the faster reaction time, it allows an easier control of what is normally difficult to control Suspension polymerization reaction.

Preferred embodiment of the invention

As has been mentioned, it is well known to use vinyl chloride in an aqueous medium which contains at least one suspending agent contains to polymerize in suspension. A variety of suspending or suspending agents are suggested for this purpose been. It has been suggested to use water-soluble, natural ingredients with high molecular weight, such as starch, gelatin, 'Iragant gum and the like, water-soluble cellulose derivatives, such as alkyl cellulose, hydroxyalkyl cellulose and the like. There are also generally water-soluble, synthetic, high molecular weight Substances such as polyvinyl alcohol, polyacrylates, vinyl acetate, ivialeinic acid copolymers and the like, as well as water-insoluble, inorganic substances such as bentonite, talc, barium sulphate, OaI-ciumcarbonat and the like are used.

itfie previously mentioned, the "azo" catalysts U.S. Patent 2,471,959 generally on vinyl chloride polymerization used. One of these, namely 2,2'-azobis-isobutyronitrile with polyvinylpyrrolidone, leads to hard, dense ones Polymer particles as described in U.S. Patent $ 4-59,719 is; another, ABVN with sorbitan monolaurate, leads to a porous resin. It is not known why each of the aforementioned catalysts in combination with the specific surfactants Means leads to the results as it does, but they are distinctly unique and with the specific interaction of properties attributable to the specific combinations.

as long as the amount Ü.3VN that catalyzes the in question Suspension polymerization reaction is used in which Range from eU about 0.01 to about 0.1 ^ wt .- ^, based on the ge

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weight of Vi ylmonomere, can be smaller amounts of peroxy catalysts than cocatalysts in conjunction with the
ABVN can be used without reducing the porosity. So
it is useful in conjunction with ABVN less than 0.005.
Parts per 100 parts of catalysts with a short half-life, such as isopropyl peroxydicarbonate, 2-ethylhexyl peroxydicarbonate, acetyl cyclohexyl sulfonyl peroxide and the like.

It is a great advantage that one can reduce the use of suspending agents because they have well-known but little-publicized disadvantages. The use of suspending agents slows down the reaction and introduces a comparatively high level of undesirable contamination, which is in all probability after further processing of the resin
by the manufacturer who will use it to make plasticizers
to absorb, impaired. The present invention uses a much smaller amount of suspending agent in combination with a known initiator which not only increases the reaction rate, but also gives a more uniform exotherm at the higher reaction rate without loss of conversion and better porosity without a problem of settling on the heater walls When the suspension polymerization of vinyl chloride in an aqueous medium is mentioned here, not only monomeric vinyl chloride is meant, but monomer mixtures of at least 50% vinyl chloride with other vinyl monomers which are compatible and copolymerizable with vinyl chloride are also included.

The water / water monomer ratio is not critical and can vary from 1.5: 1 to about 4: 1, but preferred is a ratio in the range from 1.9: 1 to about 3: 1 (volume ratios) used.

The present process is most conveniently carried out under acidic conditions, the pH of the system in the
Range from about 4 to about 6. To get the required pH

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to maintain the system, it is generally not necessary to to add something to the system. Suitable compounds are sufficient under conditions where the addition of substances is necessary in comparatively small amounts so that they do not contaminate the end product.

The process of the invention can be carried out either batchwise or as a continuous process. One draws a batch process, using reaction vessels that can withstand the autogenous pressure exerted by the vapor of the vinyl chloride monomer under the 'temperature conditions the response is developed. i) ie! color of the product is superior to that of the product formed by known processes because of lower levels of secondary surfactant Funds are in place.

Porosity measurements were made with an Aminco-tiiinslow porosimeter, which is a mercury intrusion device. The way it works is similar to the AtiTM D-2873. Measurements made with this instrument are on the ability of PVC to plasticize to absorb, related. Higher particle porosity leads to shorter drying times.

The invention is further illustrated by the following examples in which all parts and percentages are by weight unless otherwise noted.

example 1

200 parts of deionized water and 0.3 parts of sorbitol an-monolaurate, 0.07 Parts of methyl cellulose and 0.035 parts of ABVN per 100 parts of resin to be subsequently poured in. The temperature of the contents of the reaction vessel is raised to 50 s ⁰ O (122 ° i ') and the circulation of heat transfer medium in the jacket of Reaktionsbehälteis is adjusted to the temperature of the reaction at 0 to 50

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keep. The reaction vessel is purged with vinyl chloride vapor, and then 100 parts of liquid vinyl chloride monomer iii is added to the reaction vessel while stirring continuously. The reaction is so far completed on üinde of 14.5 hours means that about 92 ~ / o are umgevwandelt of the monomer into individual polymer particles, which are then pressed out of the reaction vessel, centrifuged and dried. Measurement of the porosity of the resin with an Aminco-liinslow porosimeter shows that the porosity is 0.4-52 ecm per g.

Example 2

The procedure of Example 1 is followed, with the difference that 0.30 parts of lauroyl peroxide per 100 parts of vinyl chloride are used as a catalyst can be used instead of ABVN. A measurement of the porosity of the dried, particulate, polymer Product showed a porosity of 0.419 ecm per gram and one

Response time of 14/2 {hours.

From the two previous examples it can be seen that the increased porosity is not obtained with lauroyl peroxide instead of ABVN will.

Example 3

The procedure of Example 1 above was followed, with the difference that the amount of sorbitan monolaurate was halved became; This is because only 0.15 part of öorbitan monolaurate per 100 parts was filled into the reaction vessel. The response time was 12.25 hours and the porosity of the dried polymeric product was 0.423 cm per gram. This shows that with half the amount of surfactant and, when using ABVIM instead of lauroyl peroxide, an increase in porosity be obtained '-: ann. The results are summarized below.

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Tabel ABVN I. porosity reaction öorbitan- Lauroyl (phr) (ccm / g) (fcj.tdn.) monolaurate peroxide 0.035 0.452 14.50 (pnr) (phr). - 0.419 14.50 0.30 - 0.035 0.423 12.25 0.30 0.30 _ 0.367 15.75 0.15 - 0.15 0.30

All reaction times' were after conversion of 92% of the Reaction container filled monomers indicated. It can be seen that the reaction time decreased as the amount of surfactant increased Agent has been decreased, an indication that the surfactant may act as an inhibitor that slows the response. In addition, using the smaller amount of surfactant, the color of the product was good better than the product in the other examples, surprisingly are with 0.15 P & r sorbitan monolaurate, but are used of lauroyl peroxide for ABVH the reaction rates no better and the color of the product is; not so good.

The previous examples using the combination of ABVN and borbitan monolaurate were repeated with the difference that in addition to the ABVN, smaller amounts of lauroyl peroxide, not more than 0.1 part, and smaller amounts Isopropyl peroxydicarbonate, not more than 0.005 parts per 100 parts resin, was added to the contents of the reaction vessel became. The porosity was essentially unchanged and the smaller amounts of peroxy catalysts affected the color of the polymeric end product is not disadvantageous.

Example 4

In a 227 liter fasting, glass-lined, encased An autoclave fitted with a stirrer can be used 200 parts deionized water, 0.07 part methyl cellulose,

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0.02 parts. ABViY and 0.004 parts of isopropyl peroxydicarbonate (also referred to as IPP) were filled. No second surfactant is added to the reactor. The temperature of the contents of the reaction vessel is increased to. Increases 55 ° C (131 ⁰ F ¹ and adjusting the circulation of heat transfer medium in the jacket of the reaction vessel to keep the temperature of the fieaktionsbehälters at 55 C. The reaction container is purged with vinyl chloride vapor and then 100 parts of liquid Vinylchioridmonomeres into the reaction vessel The reaction is so far complete at the end of 9 hours that about 92/0 of the monomer has converted into individual polymeric particles, which are then pressed out of the reaction vessel, centrifuged and dried des Harzes with an AmiPso-Winslow porosimeter showed that the porosity is 0.34-7 ccm / g.

Example 5

The same procedure is used as has been described above in Example 4, with the difference that the catalyst used consists of 0.12 part of lauroyl peroxide and 0.004 part of IPP. The reaction is carried out at 55 ⁰ O (131 ⁰ J ¹ ) and is addressed as complete after 11 hours. 9270 of the final monomer have reacted and the porosity of the product is 0.224 ccm / g.

It is noted that the porosity of the resin using ABYU without a second surfactant is unexpectedly higher than the porosity obtained with the lauroyl peroxide catalyst. Although it is apparent that higher porosities than 0.34-7 cc / g can be obtained by the procedure described in Example 1 above, the PVC resin obtained using ABVN without a second surfactant is suitable for many industrial dry mix applications. Uses sufficiently porous. As a comparison, the porosity γοη O ₉ ccm / g is too low for dry mix application

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In summary, the invention thus relates to a suspension polymerization process for the production of highly porous polyvinyl chloride resin particles with a comparatively narrow pore size distribution through the use of a combination of J ^, ^ '-ezobis (^,) f-dimethylvaleronitrile) and öorbitan monolaurate, optionally in conjunction with smaller amounts of lauroyl peroxide, isopropyl peroxydicarbonate and other catalysts known for the suspension polymerization of polyvinyl chloride resin without dispensing with vinyl chloride conversion. moderately porous
Polyvinyl chloride resin is made by using a critical one
Amount of Js. , ς ^ '- Azobis (, ^, ^ - dimethylvaleronitrile) produced alone under specific process conditions.

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Claims (5)

- 11 claims dl A method of making a porous vinyl chloride polymer having a narrow distribution of pore sizes and an average pore size in the range of about 0.3 to about 0.5 microns, characterized in that an agitated aqueous suspension of vinyl chloride monomers in the presence of about 0.002 to about 0.2 wt .- / ^, ^ '- Azobis (Jv, iT-dimethylvaleronitrile), based on the weight of vinyl chloride monomer, and less?,. Ls about 0.4 wt .-; o Borbitan monolaurate, based on the weight of vinyl chloride monomer, heated at a temperature in the range of about 27 ° G (80 ⁰ B ¹ ) to about 66 ° 0 (150 ° F) for a time sufficient to convert over 70 % of the monomer into a polymer, which has a porosity in the range of about 0.33 to about 0.50 cc / g. 2. The method according to claim 1, characterized in that said ^, ^ ¹ -azobisQ ^ Jf-dimethylvaleronitrile) is present in an amount in the range of 0.01 to 0.15 wt. -70, based on the weight of the vinyl chloride monomer, said 8orbitan monolaurate is present in the range of about 0.1 to about 0.3 '/ ° t based on the weight of the vinyl chloride monomer, that the temperature is in the range of about 43 ⁰ G (110 ⁰ I ¹ ) to about 60 ° C (140 ⁰ F) and the porosity of the polymer in the range of about 0.4 to about 0.50 cc / g. 3. The method according to claim 1 or 2, characterized in that over 90 / e of the I / ionomer are converted into polymer. 4. A method of making a vinyl chloride polymer in the form of a porous, spherical particle having a porosity in the range of about 0.33 to about 0.50 cc / g by heating an agitated aqueous suspension of vinyl monomer and a catalyst at a temperature in the range from about 27 ° 0 (80 ⁰ F) to about 66 ⁰ O '(150 ⁰ F), characterized in that the »suspension polymerization is essentially carried out in the presence of about 0.002 to about 0.2 wt .- ^ A Λ ' - ^A 209846/1083 Azobis (, ^,) f-dimethylvaleronitrile), bo absorbed to the weight of Vin.rlcnloridmonomerei, and less than about 0.4 wt .-, ο corbitan monolaurate, based on the weight of vinyl chloride monomer, executes to L'ber 70 ■■> to convert the coiiomer into polymer. 5. Yeriahren according to .- ^ nspruch 4, characterized in that one the ouspensionpoljiaerisierung in the presence of about 0.1 up to about 0.15 Ge ^ .- :; 6 \, ^ --Azobi, s (^, jf-dimethylvaleronitrile) and from about 0.1 to about 0.1 > wt .-, · - .oorbitane monolaurate ,. beiso ^^ en on the weight of '/ inylchloridmoiioiaerem, running to about 90 / f of the ivionomer umzuwmideln in Pol./meres. 2098A6 / 10fi3